netdev - Re: [PATCH net v2 3/3] r8152: Choose our USB config with choose

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Date: Fri, 1 Dec 2023 22:28:11 -0800
From: Grant Grundler <grundler@...omium.org>
To: Douglas Anderson <dianders@...omium.org>
Cc: linux-usb@...r.kernel.org, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"David S . Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Grant Grundler <grundler@...omium.org>, Hayes Wang <hayeswang@...ltek.com>, 
	Simon Horman <horms@...nel.org>, Bjørn Mork <bjorn@...k.no>, 
	netdev@...r.kernel.org, Brian Geffon <bgeffon@...gle.com>, 
	Alan Stern <stern@...land.harvard.edu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2 3/3] r8152: Choose our USB config with
 choose_configuration() rather than probe()

On Fri, Dec 1, 2023 at 10:31 AM Douglas Anderson <dianders@...omium.org> wrote:
>
> If you deauthorize the r8152 device (by writing 0 to the "authorized"
> field in sysfs) and then reauthorize it (by writing a 1) then it no
> longer works. This is because when you do the above we lose the
> special configuration that we set in rtl8152_cfgselector_probe().
> Deauthorizing causes the config to be set to -1 and then reauthorizing
> runs the default logic for choosing the best config.
>
> I made an attempt to fix it so that the config is kept across
> deauthorizing / reauthorizing [1] but it was a bit ugly.
>
> Let's instead use the new USB core feature to override
> choose_configuration().
>
> This patch relies upon the patches ("usb: core: Don't force USB
> generic_subclass drivers to define probe()") and ("usb: core: Allow
> subclassed USB drivers to override usb_choose_configuration()")
>
> [1] https://lore.kernel.org/r/20231130154337.1.Ie00e07f07f87149c9ce0b27ae4e26991d307e14b@changeid
>
> Fixes: ec51fbd1b8a2 ("r8152: add USB device driver for config selection")
> Suggested-by: Alan Stern <stern@...land.harvard.edu>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Grant Grundler <grundler@...omium.org>

> ---
>
> Changes in v2:
> - ("Choose our USB config with choose_configuration()...) new for v2.
>
>  drivers/net/usb/r8152.c | 16 +++++-----------
>  1 file changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index 2c5c1e91ded6..0da723d11326 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -10053,7 +10053,7 @@ static struct usb_driver rtl8152_driver = {
>         .disable_hub_initiated_lpm = 1,
>  };
>
> -static int rtl8152_cfgselector_probe(struct usb_device *udev)
> +static int rtl8152_cfgselector_choose_configuration(struct usb_device *udev)
>  {
>         struct usb_host_config *c;
>         int i, num_configs;
> @@ -10080,19 +10080,13 @@ static int rtl8152_cfgselector_probe(struct usb_device *udev)
>         if (i == num_configs)
>                 return -ENODEV;
>
> -       if (usb_set_configuration(udev, c->desc.bConfigurationValue)) {
> -               dev_err(&udev->dev, "Failed to set configuration %d\n",
> -                       c->desc.bConfigurationValue);
> -               return -ENODEV;
> -       }
> -
> -       return 0;
> +       return c->desc.bConfigurationValue;
>  }
>
>  static struct usb_device_driver rtl8152_cfgselector_driver = {
> -       .name =         MODULENAME "-cfgselector",
> -       .probe =        rtl8152_cfgselector_probe,
> -       .id_table =     rtl8152_table,
> +       .name = MODULENAME "-cfgselector",
> +       .choose_configuration = rtl8152_cfgselector_choose_configuration,
> +       .id_table = rtl8152_table,
>         .generic_subclass = 1,
>         .supports_autosuspend = 1,
>  };
> --
> 2.43.0.rc2.451.g8631bc7472-goog
>